T5688: Changed 'range' to multi in 'client-ip-pool' for accell-ppp
Changed node 'range' to multi in 'client-ip-pool' for accell-ppp
services.
Added completionHelp to default-pool and next-pool.
Fixed verification in vpn l2tp config script.
(cherry picked from commit 4ffec67d04670192d9b722353cbaef04cb0ba129)